Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. Via the keyboard device, characters and symbols can be inputted into the computer system directly. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboard devices. The keyboard devices are classified into two types, i.e. the keyboard devices for desktop computers and the keyboard modules for notebook computers.
FIG. 1 is a schematic top view illustrating the outer appearance of a conventional keyboard module. As shown in FIG. 1, there are plural keys 10 on a surface of the conventional keyboard module 1. These keys 10 are classified into several types, e.g. ordinary keys 101, numeric keys 102 and function keys 103. When one of these keys 10 is depressed by the user's finger, a corresponding signal is issued to the computer, and thus the computer executes a function corresponding to the depressed key. For example, when an ordinary key 101 is depressed, a corresponding English letter or symbol is inputted into the computer. When a numeric key 102 is depressed, a corresponding number is inputted into the computer. In addition, the function keys 103 (F1˜F12) can be programmed to provide various functions. The conventional keyboard module 1 is a keyboard device for a notebook computer.
Hereinafter, the inner structure of a conventional keyboard module will be illustrated in more details. FIG. 2 is a schematic cross-sectional view illustrating a conventional keyboard module. As shown in FIG. 2, the conventional keyboard module 2 comprises plural keys 20, a membrane switch circuit member 21 and a bottom plate 22. Each key 20 comprises a keycap 201, a scissors-type connecting element 202 and an elastic element 203. From top to bottom, the keycap 201, the scissors-type connecting element 202, the elastic element 203, the membrane switch circuit member 21 and the bottom plate 22 of the conventional keyboard module 2 are sequentially shown. The bottom plate 22 is used for supporting the keycaps 201, the scissors-type connecting elements 202, the elastic elements 203 and the membrane switch circuit member 21. For supporting these components, the bottom plate 22 is preferably made of a metallic material in order to provide the stronger structural strength. The conventional keyboard module 2 is a keyboard device for a notebook computer (not shown).
In the key 20, the keycap 201 is exposed outside the conventional luminous keyboard module 2, so that the keycap 201 can be depressed by the user. The scissors-type connecting element 202 is used for connecting the keycap 201 and the bottom plate 22. The elastic element 203 is penetrated through the scissors-type connecting element 202. In addition, both ends of the elastic element 203 are contacted with the keycap 201 and the membrane switch circuit member 21, respectively. The membrane switch circuit member 21 comprises an upper wiring board 211, a spacer layer 212, and a lower wiring board 213. The upper wiring board 211 has plural upper contacts 2111. The spacer layer 212 is disposed under the upper wiring board 211, and comprises plural perforations 2121 corresponding to the plural upper contacts 2111. The lower wiring board 213 is disposed under the spacer layer 212, and comprises plural lower contacts 2131 corresponding to the plural upper contacts 2111. The plural lower contacts 2131 and the plural upper contacts 2111 are collectively defined as plural key switches 214.
Recently, the general trends in designing electronic devices are toward slimness and light weightiness, and thus the conventional keyboard module needs to meet the requirements of slimness. For achieving this purpose, the manufacturers of the keyboard modules make efforts in minimizing the thickness of the keyboard modules. In accordance with the conventional approach, the thicknesses of the components (especially the bottom plate) of the keyboard module should be as small as possible. In addition to the reduction of the thickness of the bottom plate, another approach is to produce a keyboard module with a lighter bottom plate. For example, the bottom plate is made of aluminum. Although the use of the lighter bottom plate is effective to reduce the weight of the bottom plate, the structural strength of the aluminum bottom plate is weak. Consequently, the aluminum bottom plate is readily suffered from damage during the mold forming process.
Moreover, since the thickness of the electronic device is reduced, the inner space of the electronic device is reduced. Owing to the small inner space, some manufacturers of the keyboard modules may reduce the number of heat dissipating modules. Under this circumstance, the heat-dissipating efficiency is impaired.
Therefore, there is a need of providing an improved slim-type keyboard module in order to overcome the above drawbacks.